1. Field of the Application
The application relates in general to a LED (Light Emitting Diode) driver of current-driven devices, and more particularly, to a driving circuit of current-driven devices, which can determine whether the output channel is available for power-saving and control the output voltage. accurately
2. Description of the Related Art
A light emitting diode (LED) has advantages of low power consumption, long lifetime, small volume and short response time. Therefore, the LED increasingly is adopted on the conventional lamp bulb. Besides, the LED can also be applied in domestic electric appliances and used as a backlight source for a notebook computer. Compared with a notebook computer using cold-cathode-fluorescence lamps (CCFLs), the notebook compute using LEDs can save more power and elongate lifetime of the battery.
This kind of electronic device (such as a notebook computer) includes an LED driving circuit for driving the LEDs. Normally, the electronic device is configured with a number of LED channels, but sometimes, a part of which are not used and set at a floating state. If there is no good mechanism for detecting which LED channels are at floating state and accordingly controlling the floating-state LED channels, the floating-state LED channels easily cause unnecessary power consumptions, influence conversion efficiency of the whole circuit and increase power consumption, or even cause an error determination and operation of the DC-DC converter.
For this reason, an example of the invention provides a driving circuit which can detect whether the LED channels are enabled or disabled at the initiation. Accordingly, the LED driver can turn off the disabled LED channels and ignore the feedback status thereof in order to save power, increase conversion efficiency of the whole circuit, and reduce the error determination to make the DC-DC converter in normal operation.